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MARGO - Multiproxy Approach for the Reconstruction of the Glacial Ocean surface

The MARGO initiative was supported by IMAGES and by PAGES and ran from approximately 1999 - 2009.

The acronym MARGO is short for "Multiproxy Approach for the Reconstruction of the Glacial Ocean surface". MARGO was an international community effort of more than 50 scientists, who pursued the goal of reconstructing the sea-surface temperature at the Last Glacial Maximum with the best methods available: methods based on species composition of micro fossils and geochemical methods.

Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s. But, several shortcomings with that earlier effort became apparent. MARGO synthesized sea surface temperatures during the Last Glacial Maximum (rigorously defined as the period between 23 and 19 thousand years before present), integrating microfossil and geochemical reconstructions of surface temperatures and including assessments of the reliability of individual records.

Scientific objectives

MARGO's stated objectives were to:

- compile consistent "microfossil assemblage" and other proxy data sets (core tops + LGM) to be used in a second step to reconstruct SST, sea ice, etc., based on various statistical techniques and geochemical equations;

- apply different "microfossil assemblage" - based techniques and geochemical equations to the newly compiled data sets in order to reconstruct a suite of solutions for LGM SST and d18O(water) on basin-wide and global scales;

- map the differences and similarities between the results of different SST approaches, in comparison with the d18O distribution for LGM conditions.

This map shows the reconstructed LGM sea-surface temperature anomaly, computed as the difference between the Last Glacial Maximum (LGM, between 19,000 and 23,000 years before present) and present day, in units of °C for the Northern Hemisphere winter season (January-February-March). Negative anomalies (blue) denote regions that according to the MARGO reconstruction were colder than today, positive anomalies (yellow) point to regions that might have been warmer than today. The squares mark the geographic locations of the sediment cores that were investigated by the MARGO project using a variety of methods for temperature reconstruction. Dark grey areas in the ocean stand in for those regions to which no anomaly could be assigned because the nearest data points were too far (more than 2000 km) away. For illustration, contour lines on land (height contours with a 500 m interval) indicate the extent of the continental ice sheets. The grid lines are 30° of longitude and latitude apart. For the map an equal-area Hammer projection was chosen. (Nature Geoscience, 2009)